The statements in this section merely provide background information related to the present disclosure. Accordingly, such statements are not intended to constitute an admission of prior art.
Catalytic converter devices are employed in exhaust systems of internal combustion engines to promote oxidation or reduction of combustion products in an exhaust gas feedstream. Catalytic converter devices employ metallic or ceramic support substrates on which washcoat materials including catalysts may be applied. Catalysts include catalytic materials preferably combined with catalyst support materials. Catalytic materials include platinum-group metals of platinum, palladium, rhodium, gold and silver, and base metals including iron, copper, tin, and others. Catalyst support materials include alumina, e.g., Al2O3 and zeolite, e.g., SiC.
Processes for preparing catalysts include such steps as preparing materials containing catalytic materials, adding catalytic materials to a solution containing catalyst support materials, and precipitating out a resultant catalyst that may be calcined.
Materials in the form of a washcoat slurry containing the calcined catalyst may be applied to a substrate by immersion or another suitable method. The resulting coated substrate may be calcined for a period of time to prepare a finished product suitable for assembly into a catalytic converter assembly.
Compression-ignition and lean-burn spark-ignition engines operate at relatively low exhaust gas temperatures, often near 200° C., with corresponding need to have exhaust aftertreatment devices that are configured to operate at such temperature ranges.